Yii2 XSS 防范策略

XSS 漏洞修复

原则：　不相信客户输入的数据
注意: 攻击代码不一定在《script》《/script》中

• 将重要的cookie标记为http only, 这样的话Javascript 中的document.cookie语句就不能获取到cookie了.
  
• 只允许用户输入我们期望的数据。 例如：　年龄的textbox中，只允许用户输入数字。 而数字之外的字符都过滤掉。
  
• 对数据进行Html Encode 处理
  
• 过滤或移除特殊的Html标签， 例如: script, iframe , < for <, > for >, " for
  
• 过滤JavaScript 事件的标签。例如 "οnclick=", "onfocus" 等等。

Yii中的XSS防范

<h2>Profile of  echo CHtml::encode($user->name) ?>h2>

此方法的源码：

    /**
     * Encodes special characters into HTML entities.
     * The [[\yii\base\Application::charset|application charset]] will be used for encoding.
     * @param string $content the content to be encoded
     * @param boolean $doubleEncode whether to encode HTML entities in `$content`. If false,
     * HTML entities in `$content` will not be further encoded.
     * @return string the encoded content
     * @see decode()
     * @see http://www.php.net/manual/en/function.htmlspecialchars.php
     */
    public static function encode($content, $doubleEncode = true)
    {
        return htmlspecialchars($content, ENT_QUOTES | ENT_SUBSTITUTE, Yii::$app->charset, $doubleEncode);
    }

htmlspecialchars & htmlentities & urlencode 三者的区别

http://php.net/manual/zh/function.htmlspecialchars.php
http://php.net/manual/zh/function.htmlentities.php
http://cn2.php.net/manual/zh/function.urlencode.php

Available flags constants
Constant Name	Description
ENT_COMPAT	Will convert double-quotes and leave single-quotes alone.
ENT_QUOTES	Will convert both double and single quotes.
ENT_NOQUOTES	Will leave both double and single quotes unconverted.
ENT_IGNORE	Silently discard invalid code unit sequences instead of returning an empty string. Using this flag is discouraged as it » may have security implications.
ENT_SUBSTITUTE	Replace invalid code unit sequences with a Unicode Replacement Character U+FFFD (UTF-8) or &#FFFD; (otherwise) instead of returning an empty string.
ENT_DISALLOWED	Replace invalid code points for the given document type with a Unicode Replacement Character U+FFFD (UTF-8) or &#FFFD; (otherwise) instead of leaving them as is. This may be useful, for instance, to ensure the well-formedness of XML documents with embedded external content.
ENT_HTML401	Handle code as HTML 4.01.
ENT_XML1	Handle code as XML 1.
ENT_XHTML	Handle code as XHTML.
ENT_HTML5	Handle code as HTML 5.

htmlspecialchars

Convert special characters to HTML entities

string htmlspecialchars ( 
            string $string 
            [, int $flags = ENT_COMPAT | ENT_HTML401 
            [, string $encoding = ini_get("default_charset") 
            [, bool $double_encode = true ]
        ]
    ] 
)

The translations performed are:

• & (ampersand) becomes &
  
• " (double quote) becomes " when ENT_NOQUOTES is not set.
  
• ' (single quote) becomes ' (or ') only when ENT_QUOTES is set.
  
• < (less than) becomes <
  
• > (greater than) becomes >

$new = htmlspecialchars("Test", ENT_QUOTES);
echo $new; // <a href='test'>Test</a>
?>

htmlentities

Convert all applicable characters to HTML entities

string htmlentities ( 
            string $string 
            [, int $flags = ENT_COMPAT | ENT_HTML401 
            [, string $encoding = ini_get("default_charset") 
            [, bool $double_encode = true ]
        ]
    ] 
)

$str = "A 'quote' is bold";

// Outputs: A 'quote' is <b>bold</b>
echo htmlentities($str);

// Outputs: A 'quote' is <b>bold</b>
echo htmlentities($str, ENT_QUOTES);
?>

urlencode

URL 编码是为了符合url的规范。因为在标准的url规范中中文和很多的字符是不允许出现在url中的。
例如在baidu中搜索"测试汉字"。 URL会变成
http://www.baidu.com/s?wd=%B2%E2%CA%D4%BA%BA%D7%D6&rsv_bp=0&rsv_spt=3&inputT=7477
所谓URL编码就是：　把所有非字母数字字符都将被替换成百分号（%）后跟两位十六进制数，空格则编码为加号（+）
　此字符串中除了 -_. 之外的所有非字母数字字符都将被替换成百分号（%）后跟两位十六进制数，空格则编码为加号（+）。此编码与 WWW 表单 POST 数据的编码方式是一样的，同时与 application/x-www-form-urlencoded 的媒体类型编码方式一样。由于历史原因，此编码在将空格编码为加号（+）方面与 RFC1738 编码（参见 rawurlencode()）不同。

echo '$userinput), '">';
?>


$query_string = 'foo=' . urlencode($foo) . '&bar=' . urlencode($bar);
echo '$query_string) . '">';
?>